Photo courtesy San Diego Zoo Global
Recovery efforts for the federally endangered Southern California population of mountain yellow-legged frogs (Rana muscosa) moved forward with the release of over 250 froglets by San Diego Zoo Global to their historic range in the San Bernardino National Forest on Tuesday, June 19. More releases of the species in the forest, as well as in neighboring Angeles National Forest, are scheduled for later in the summer.
The regional effort is the product of collaboration between San Diego Zoo Global, Los Angeles Zoo, Henry Doorly Zoo, California Department of Fish and Wildlife, U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Forest Service and others. The frogs are being bred in captivity at the zoos and reintroduced to their native streams in the San Bernardino, San Gabriel and San Jacinto mountains.
In 2002, when the frogs were listed under the Endangered Species Act, it was estimated that fewer than 100 adult frogs remained in the wild. Threats to the species include habitat loss, pollution, non-native predators and the deadly amphibian disease chytridiomycosis, which is caused by chytrid fungus. Scientists determined that captive rearing offered the species the best chance of recovery. Other measures being taken to help the species include removal of non-native fish and bullfrogs from streams and conducting research to inform recovery actions.
To that end, Debra Shier, associate director of recovery ecology at the San Diego Zoo Global, and her team are conducting research on the froglets released Tuesday. About half were “soft-released,” held and fed in acclimation cages in the stream for one week, while the other half were “hard-released,” transferred to the stream yesterday and immediately released. The goal is to develop a strategy to reduce post-release movement which increases mortality. Each week, Shier and her team will be monitoring the frogs, which were individually marked.
Recovery efforts, now in their 12th year, have resulted in more than 4,000 frogs released into their historic range. Breeding at two sites in the San Bernardino Mountains have been observed in post-release surveys by USGS.
A draft recovery plan for this species from the U.S. Fish and Wildlife Service is expected to be released for public review and comment in the near future.
